1. Field of the Invention
The invention relates to the production of textured surfaces for medical, industrial, and commercial applications and is directed more particularly to surfaces having undercut micro recesses.
2. Description of the Prior Art
It is known to use textured surfaces on surgical implants for the purpose of encouraging bone adhesion and thus stabilizing the location of the implant relative to the bone. For example, in an artificial hip, including a femoral sub-assembly for positioning in a patient's femur, and an acetabular sub-assembly for positioning in the patient's acetabulum, the femoral sub-assembly includes an artificial stem which is typically provided with a textured surface, and the acetabular sub-assembly includes an acetabular cup which is typically provided with a textured surface, the textured surfaces being provided to promote bone in-growth.
The desirability of roughened, textured, bone-engaging surfaces to assure stable positioning of surgical implants has been recognized in U.S. Pat. No. 5,298,115, issued Mar. 29, 1994, in the name of Ian Leonard, U.S. Pat. No. 5,456,723, issued Oct. 10, 1995, in the name of Samuel G. Steinemann, U.S. Pat. No., 5,603,338, issued Feb. 18, 1997, in the name of Keith D. Beaty, U.S. Pat. No. 5,853,561, issued Dec. 29, 1998, in the name of Bruce A. Banks, and U.S. Pat. No. 5,965,006, issued Oct. 12, 1999, in the names of Roland Baege et al.
To produce such textured surfaces, one known method is to provide a mass of titanium spheres vacuum fused onto the datum surface of the implant. This method is described in U.S. Pat. No. 4,834,756, issued May 30, 1989, to Robert V. Kenna. In a similar procedure, described in U.S. Pat. No. 4,644,942, issued Feb. 24, 1987 to Kenneth R. Sump, an extractable component and titanium spheres are densified as a coating, which is fused onto a datum surface of the implant, and the extractable component subsequently is extracted. While an improvement over untreated metal, questions have arisen over the longevity of usefulness of the implanted devices utilizing such surfaces. It is questionable whether there is substantial genuine adhesion. It is believed that the voids formed by the spheres are not sufficient for long-term nourishment of ingrowing tissue and/or bone. Further, there have been failures of prosthetics treated in this manner because of the fusing process adversely affecting metallurgical properties. of the implant material, and because of difficulties in removing manufacturing contaminants, such as cutting oils, from the fused sphere network. Still further, the original datum surface, which can be accurately determined, is lost by the application of the coating spheres.
The formation of perforated thin metallic sheets or plates by means of chemical milling and/or photo-chemical etching techniques has been described in U.S. Pat. No. 3,359,192, issued Dec. 19, 1967, in the names of Hans-Joachim Heinrich et al., U.S. Pat. No. 5,606,589, issued Feb. 25, 1997, in the names of Anthony J. Pellegrino et al., and U.S. Pat. No. 5,814,235, issued Sep. 29, 1998, in the names of Anthony J. Pellegrino et al. The processes therein described have been found lacking in precise control over the degree and extent of roughness or texturing.